1. Field of the Invention
The present invention relates to a data processing system and a data processing method for applying to an image formation apparatus and an image formation method according to which a print head that can jet ink is allowed to scan the same printing region on a printing medium a plurality of times to perform a printing operation to thereby complete an image to the same printing region.
2. Description of the Related Art
In the proof system to confirm an image to be printed through a printer, a Raster Image Processor (RIP) is used to output image data subjected to separation and binarization through a flat-bed machine, a digital color press (DCP), or an inkjet printer for example.
The proof system using an inkjet printer is classified to a proof system combined with RIP and a proof system as in a newspaper proof system where a combination of exclusive software application and a printer is used to perform proofreading. In the latter proof system,an image is subjected to binarization and development by RIP and exclusive solution software developed by a software vendor different from the printer maker and is sent and outputted to a printer. Generally, in the proof system as described above, an amplitude modulation (AM) screen (hereinafter halftone dots), which is the binarization as in the offset printing, is used to realize the same image texture as that in the formal printing. The halftone dots in the offset printing of the formal printing have different resolutions (e.g., 45 lpi, 85 lpi, 175 lpi) and are used depending on a purpose. Thus, the proof system is also required to realize the printing at the same resolution as that of the halftone dots in the formal printing.
On the other hand, in a printing apparatus having a print head including a plurality of printing elements (e.g., an inkjet printer), the binarization of a document image or a photograph image is carried out by the error diffusion method having a high dispersibility. In the case of the inkjet printer, the printed image quality significantly depends on the performance of the print head itself. For example, a printed image includes uneven density depending on the ink ejecting amount or direction. In order to solve this disadvantage, Japanese Patent Laid-Open No. 2002-096455 suggests a multipass printing method. In the multipass printing method, the main scanning is performed a plurality of times in the same main scanning region on a printing medium to thereby form an image. In each main scanning (pass), a thinned image is formed based on a culling mask pattern data (pass mask) to thereby complete an image.
The thinning pattern (pass mask) used in the inkjet printer based on the multipass printing method is generally designed so that, from the viewpoint of the resistance to the landing accuracy of the print head, the layout of dots on the printing medium after the thinning operation is optimal to the final image quality. Thus, such a thinning pattern is used that is optimized to the dot pattern before the thinning operation prepared by the binarization method having a layout of highly-dispersed dots. However, when the thinning pattern that is optimized to the dot pattern prepared by the binarization method having a layout of highly-dispersed dots as described above is used to thin the image binarized by regular halftone dots, the dot layout may have a reduced dispersibility. Specifically, when such a thinning pattern is used that is not preferable to the inputted halftone dot image, a landing variation causes the image formed on the printing medium to be deteriorated due to uneven density or uneven lines.
In order to solve the above disadvantage, an approach can be used to store, in a printer in advance, halftone dot thinning patterns classified based on the binarization method (e.g., printing mode, resolution, or screen angle) so that an appropriate pattern can be specified and used for an actual printing. However, this approach causes an extreme complexity. The reason is that RIP or exclusive software solution makers in the case require huge trials and errors in addition to the understanding of the internal sequence of the printer to select an appropriate thinning pattern.